Page 13 - Manual – Dehumidifier G21 – Impact 20

containing flammable refrigerants the system shall be purged with oxygen-free nitrogen to render
the appliance safe for flammable refrigerants. This process may need to be repeated several times.
Compressed air or oxygen shall not be used for purging refrigerant systems.
For appliances containing flammable refrigerants, refrigerants purging shall be achieved by
breaking the vacuum in the system with oxygen-free nitrogen and continuing to fill until the working
pressure is achieved, then venting to atmosphere, and finally pulling down to a vacuum. This
process shall be repeated until no refrigerant is within the system. When the final oxygen-free
nitrogen charge is used, the system shall be vented down to atmospheric pressure to enable work
to take place. This operation is absolutely vital if brazing operations on the pipe-work are to take
place.
Ensure that the outlet for the vacuum pump is not close to any potential ignition sources and that
ventilation is available.
1. Charging procedures
In addition to conventional charging procedures, the following requirements shall be followed.
• Ensure that contamination of different refrigerants does not occur when using charging
equipment. Hoses or lines shall be as short as possible to minimise the amount of refrigerant
contained in them.
• Cylinders shall be kept in an appropriate position according to the instructions.
• Ensure that the refrigerating system is earthed prior to charging the system with refrigerant.
• Label the system when charging is complete (if not already).
• Extreme care shall be taken not to overfill the refrigerating system.
Prior to recharging the system, it shall be pressure-tested with the appropriate purging gas. The
system shall be leak-tested on completion of charging but prior to commissioning. A follow up leak
test shall be carried out prior to leaving the site.
2. Decommissioning
Before carrying out this procedure, it is essential that the technician is completely familiar with the
equipment and all its detail. It is recommended good practice that all refrigerants are recovered
safely. Prior to the task being carried out, an oil and refrigerant sample shall be taken in case
analysis is required prior to re-use of recovered refrigerant. It is essential that electrical power is
available before the task is commenced.
a) Become familiar with the equipment and its operation.
b) Isolate system electrically.
c) Before attempting the procedure, ensure that:
» mechanical handling equipment is available, if required, for handling refrigerant cylinders;
» all personal protective equipment is available and being used correctly;
» the recovery process is supervised at all times by a competent person;
» recovery equipment and cylinders conform to the appropriate standards.
d) Pump down refrigerant system, if possible.
e) If a vacuum is not possible, make a manifold so that refrigerant can be removed from various
parts of the system.
f) Start the recovery machine and operate in accordance with instructions.
g) Do not overfill cylinders (no more than 80 % volume liquid charge).
h) Do not exceed the maximum working pressure of the cylinder, even temporarily.
i) When the cylinders have been filled correctly and the process completed, make sure that the
cylinders and the equipment are removed from site promptly and all isolation valves on the equi-
pment are closed off.